Restriction enzyme: Difference between revisions

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Restriction [[Endonucleases|Endonucleases]] cut [[DNA|DNA]] at a specific sequence, normally 4, 6 or 8 bases long. They recognise specific [[Palindromic base sequences|palindromic base sequences]] in [[DNA|DNA]] and are used to selectively cut DNA into defined fragments at sites known as '[[Restriction site|restriction sites]]'. Different restriction nucleases are obtained and purified from different species of bacteria. These [[Enzymes|enzymes]] are made in [[Bacteria|bacteria]] to degrade viral DNA. Cutting&nbsp;[[DNA]] with restriction enzymes can produce&nbsp;fragments with either [[Blunt ends|blunt]] or [[‘sticky’ ends|sticky ends]]. Different restriction enzymes recognise different DNA sequences.<br>  
Restriction [[Endonucleases|Endonucleases]]&nbsp;recognise and cut [[DNA|DNA]] at a specific plaindromic base sequences, normally 4, 6 or 8 bases long,&nbsp;and are used to selectively cut DNA into defined fragments at sites known as '[[Restriction site|restriction sites]]'. Different restriction endonucleases are obtained and purified from different species of bacteria. These [[Enzymes|enzymes]] are made in [[Bacteria|bacteria]] to degrade viral DNA. Cutting&nbsp;[[DNA]] with restriction enzymes can produce&nbsp;fragments with either [[Blunt ends|blunt]] or [[‘sticky’ ends|sticky ends]]. Different restriction enzymes recognise different DNA sequences.<br>  


Examples of restriction endonucleases are:  
Examples of restriction endonucleases are:  


*[[EcoRI|''Eco''RI]]- recognises the sequence GAATTC  
*[[EcoRI|''Eco''RI]]- recognises the sequence 5'GAATTC'3 - [[Sticky_ends|sticky ends]]&nbsp;
*[[BamHI|''Bam''HI]]- recognises the sequence GGATCC  
*[[BamHI|''Bam''HI]]- recognises the sequence 5'GGATCC'3 - [[Sticky_ends|sticky ends]]&nbsp;<br>
*[[HaeIII|''Hae''III]]- recognises the sequence GGCC
*<u>HhaI</u> - recognises the sequence 5'GCGC'3 - [[Sticky_ends|sticky ends]]
*''<u>Hpal</u>'' - recognises the sequence GTTAAC
*<u>XhoI</u> - recognises the sequence 5'CTCGAG'3 - [[Sticky_ends|sticky ends]]&nbsp;
*''<u>HindIII</u>'' - recognises the sequence AAGCTT  
*''<u>HindIII</u>'' - recognises the sequence 5'AAGCTT'3 - [[Sticky_ends|sticky ends]]&nbsp;
*''<u>PstI</u>'' - recognises the sequence CTGCAG  
*''<u>PstI</u>'' - recognises the sequence 5'CTGCAG'3 - [[Sticky_ends|sticky ends]]&nbsp;
*<u>''Sau3A''</u> - recognises the sequence GATC (produces the same [[‘sticky’_ends|sticky ends]] as [[BamHI|BamHI]] upon cutting)
*<u>''Sau3A''</u> - recognises the sequence 5'GATC'3 (produces the same [[‘sticky’ ends|sticky ends]] as [[BamHI|BamHI]] upon cutting)  
*[[HaeIII|HaeIII]]&nbsp;- recognises the sequence 5'GGCC'3 - [[Blunt_ends|blunt ends]]&nbsp;


Both ''Eco''RI and ''Bam''HI produce fragments with [[‘sticky’ ends|staggered ends]], whilst ''Hae''III produces a DNA fragment with [[Blunt ends|blunt ends]] i.e. there is no overhang.  
<br>
 
Entire genomes can be digested into defined fragments by Restriction enzymes, this is called a Restriction Digest. The number of fragments formed in a digest is dependant on 2 factors:
 
1. The restriciton enzyme used; A 4bp recogniser will statistically cut a genome in to more fragments than a 6 or 8bp recogniser because it is more likely for there to be a repeated sequence of less bp.&nbsp;
 
2. The size of the genome; Smaller genomes (10-100bp, found in viruses) give fewer fragments than larger genomes (&gt;10^6, found in e.g humans).&nbsp;<sup></sup>


<br>  
<br>  


Also see&nbsp;[[Restriction endonucleases|Restriction endonucleases]]
Also see&nbsp;[[Restriction endonucleases|Restriction endonucleases]]  
 
 
 
References&nbsp;
 
1.&nbsp;Alberts B, Johnson A, Lewis J, Raff M, Roberts K and Walter P. (2008) Molecular Biology of the Cell, Fifth Edition, New York, Garland Science.

Revision as of 13:53, 17 October 2014

Restriction Endonucleases recognise and cut DNA at a specific plaindromic base sequences, normally 4, 6 or 8 bases long, and are used to selectively cut DNA into defined fragments at sites known as 'restriction sites'. Different restriction endonucleases are obtained and purified from different species of bacteria. These enzymes are made in bacteria to degrade viral DNA. Cutting DNA with restriction enzymes can produce fragments with either blunt or sticky ends. Different restriction enzymes recognise different DNA sequences.

Examples of restriction endonucleases are:


Entire genomes can be digested into defined fragments by Restriction enzymes, this is called a Restriction Digest. The number of fragments formed in a digest is dependant on 2 factors:

1. The restriciton enzyme used; A 4bp recogniser will statistically cut a genome in to more fragments than a 6 or 8bp recogniser because it is more likely for there to be a repeated sequence of less bp. 

2. The size of the genome; Smaller genomes (10-100bp, found in viruses) give fewer fragments than larger genomes (>10^6, found in e.g humans). 


Also see Restriction endonucleases


References 

1. Alberts B, Johnson A, Lewis J, Raff M, Roberts K and Walter P. (2008) Molecular Biology of the Cell, Fifth Edition, New York, Garland Science.

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